Flexible gas hose

Quite right. There's junk and worse junk, at least all I've seen on my boat. Only place for 316 is on the guard rail, but hang on no, I've got pitting in the guard rail attachment wires and breakdown in the welds. Maybe its ok on the cleats. They are thick enough to cope with a good bit of corrosion, but don't secure them down with S/S bolts, crevice corrosion will come to play. The only S/S suitable for most uses are the rare and never-used specialist grades. It is pretty though. Chocolate fireguard pretty.
 
BigEmUp said:
Quite right. There's junk and worse junk, at least all I've seen on my boat. Only place for 316 is on the guard rail, but hang on no, I've got pitting in the guard rail attachment wires and breakdown in the welds. Maybe its ok on the cleats. They are thick enough to cope with a good bit of corrosion, but don't secure them down with S/S bolts, crevice corrosion will come to play. The only S/S suitable for most uses are the rare and never-used specialist grades. It is pretty though. Chocolate fireguard pretty.
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Anything else you don't have a clue about ?! :rolleyes:
 
Seajet said:
Anything else you don't have a clue about ?! :rolleyes:
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Well, insulting someone by suggesting they are clueless on this (or any) issue is out of order. As you clearly think you have a clue such that you can appreciate that I don't, perhaps you will correct my foolish comments.
 
BigEmUp said:
Quite right. There's junk and worse junk, at least all I've seen on my boat. Only place for 316 is on the guard rail, but hang on no, I've got pitting in the guard rail attachment wires and breakdown in the welds. Maybe its ok on the cleats. They are thick enough to cope with a good bit of corrosion, but don't secure them down with S/S bolts, crevice corrosion will come to play. The only S/S suitable for most uses are the rare and never-used specialist grades. It is pretty though. Chocolate fireguard pretty.
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Hang on then, all the expensive ss bolts I've been buying from the chandlers of late are a waste of money? I might as well have left the old mild steel stuff in place? Even when I used to know things, I later find out I knew nothing and have to remove the things which seemed to be best practise at the time. Grrr.
 
Swanrad2 said:
Hang on then, all the expensive ss bolts I've been buying from the chandlers of late are a waste of money? I might as well have left the old mild steel stuff in place? Even when I used to know things, I later find out I knew nothing and have to remove the things which seemed to be best practise at the time. Grrr.
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You are going through what I once went through. Finding out your beautiful muse isn't quite the girl you thought she was. I'm not saying it is worse than mild steel, though in some applications I think it worse than galv steel (anchors and chain).

It's fantastic stuff in the right place. Cutlery, door knobs, cooker trim etc. But on boats you've got salt everywhere, even on your hands after a wet passage and stainless hates it. Especially so in hot countries. It is an environment where you can get salty water (electrolyte) or worse, deoxygenated electrolyte which causes crevice corrosion, dissolving your bolts and chain plates and rigging in places you can't see. Elsewhere you get pitting and if under load such as with a tightened bolt you get Stress Corrosion Cracking, for which low grades of stainless like 316 is particularly vulnerable. The high grades such as duplex are much, much better and shouldn't cost a lot more. Silicon bronze, monel, inconel, hastelloy and titanium better still as examples of many alternatives. None will give these corrosion problems in any significant measure.
 
So millions of engineers who quite like stainless steel in appropriate grades and my nearly 4 decades of working in engineering are all wrong, as are my own findings in 40-plus years of boat ownership;

I don't think so, sunshine ! :rolleyes:
 
BigEmUp said:
You are going through what I once went through. Finding out your beautiful muse isn't quite the girl you thought she was. I'm not saying it is worse than mild steel, though in some applications I think it worse than galv steel (anchors and chain).

It's fantastic stuff in the right place. Cutlery, door knobs, cooker trim etc. But on boats you've got salt everywhere, even on your hands after a wet passage and stainless hates it. Especially so in hot countries. It is an environment where you can get salty water (electrolyte) or worse, deoxygenated electrolyte which causes crevice corrosion, dissolving your bolts and chain plates and rigging in places you can't see. Elsewhere you get pitting and if under load such as with a tightened bolt you get Stress Corrosion Cracking, for which low grades of stainless like 316 is particularly vulnerable. The high grades such as duplex are much, much better and shouldn't cost a lot more. Silicon bronze, monel, inconel, hastelloy and titanium better still as examples of many alternatives. None will give these corrosion problems in any significant measure.
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Whilst it is true that 316 stainless can suffer from both crevice corrosion and fatigue, these properties are well known and understood. Therefore it is not difficult to design structures and fastenings that minimise the chances that they occur in practice. The benefits of the material far outweigh the known problems which is why it is used so widely in marine applications. It is also true that there are materials that are either stronger or more corrosion resistant, but in most applications the additional benefits do not justify the additional cost.
 
Seajet said:
So millions of engineers who quite like stainless steel in appropriate grades and my nearly 4 decades of working in engineering are all wrong, as are my own findings in 40-plus years of boat ownership;

I don't think so, sunshine ! :rolleyes:
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As you correctly suggest, it is the use of the appropriate grade that counts. The best stainless grades are bullet proof. My point is 316 is the best you will usually get (or it's slightly superior variant Nitronic 50 in rod rigging) and that 316 just ain't good enough. Engineers still specifying it for chain plates and rigging amongst other things are plain wrong and that is what 40 years of experience should be telling them.

So, dear boy, when you started in engineering 40 years ago 316 was a fairly recent improvement to galv steel and a massive improvement in appearance, but now things have changed. There are plenty of far superior grades for not much more cost. It's not too late to learn some new tricks:rolleyes:
 
Tranona said:
Whilst it is true that 316 stainless can suffer from both crevice corrosion and fatigue, these properties are well known and understood. Therefore it is not difficult to design structures and fastenings that minimise the chances that they occur in practice. The benefits of the material far outweigh the known problems which is why it is used so widely in marine applications. It is also true that there are materials that are either stronger or more corrosion resistant, but in most applications the additional benefits do not justify the additional cost.
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The benefits do justify the cost. The problem is the boat builders don't look at whole of life costs. They look at customer expectation, demand and how shiny and pretty it is. If we don't demand it, it won't be fitted. Just look at the ongoing scandal over brass through hulls as a demonstration of the existence of this way of thinking. What's the cost of replacing your rig when the chain plate snaps or of re-rigging the wire or fittings after 6 years, just to be safe... Safe from what? It's to be safe from the many unnecessary and avoidable stainless steel modes of failure. Or just look at the bimini. I waste hours every several months polishing corrosion away. If 2205 were specified originally it would have cost a handful pounds more and I expect there would be no polishing ever. Work that out at even the minimum wage rates after a few decades of ownership and discount the build cost back to he original build marginal cost for its specification. And just so we stay on topic a good grade of gas hose stainless braiding wouldn't have corroded and broken my hose and put my boat at risk of blowing up. More penny wise pound foolishness.
 
So What do you suggest, titanium ?

I have a lot of that on my boat, but mainly for heat shielding not load bearing, and if one knows the material it can be nastily brittle - in the engineering sense - at times.

You mention a 6 year life for stainless ( standing rigging presumably ), but even insurers covering their backsides only mention 10 years, and a lot of knowledgable people suggest a lot longer lifespan than that.

I have to ask, why the sudden rant about one of the best marine products ever, are you selling some miracle material that's better ?! :rolleyes:
 
Seajet said:
So What do you suggest, titanium ?

I have a lot of that on my boat, but mainly for heat shielding not load bearing, and if one knows the material it can be nastily brittle - in the engineering sense - at times.

You mention a 6 year life for stainless ( standing rigging presumably ), but even insurers covering their backsides only mention 10 years, and a lot of knowledgable people suggest a lot longer lifespan than that.

I have to ask, why the sudden rant about one of the best marine products ever, are you selling some miracle material that's better ?! :rolleyes:
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Titanium is great. Horses for courses though. What use and which titanium? There are twenty odd main grades and many sub-grades. I'd go for G9 with the palladium chaser shot given money no object and for most things.

I suggest the knowledgeable people that you are referring to are missing a few things. Look at the Navtec life recommendations in their rigging service guidelines. They want you to replace your turnbuckles at 6 years. They warn about other failures at 1 or 2 years and to inspect for them. The only insurance policies I have read (Pants and RSA) by the way just require you to maintain your boat properly so it's up to you to know what to do anyway. There is no 10 year requirement.

Sudden rant follows a sudden wake up. Why is all this stuff breaking... Ah, I see now.. And it's not the best stuff ever. It's the best stuff for cutlery. For my boat it's junk, mostly and referring to the 316 grade that is everywhere.

Nope, selling nothing. How could I with so much deeply entrenched resistance anyway?
 
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